import math
x1, y1, x2, y2 = map(float, input().split())
print(f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.8f}') import math math x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 print(f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.8f}') print f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.8f}' x2, y2 = map(float, input().split()) map(float, input().split()) x2 x1, y1, x2, y2 = map(float, input().split()) map(float, input().split()) x1 y1, x2, y2 = map(float, input().split()) map(float, input().split()) y1 y2 = map(float, input().split()) map(float, input().split()) y2
import math
x1, y1, x2, y2 = map(float, input().split())
print(f'{math.sqrt((x2-x1)**2+(y2-y1)**2):.8f}')
